I think the reason why you're not getting responses is that people tend to stick with what works. People who have a solution tend not to experiment unless there's a potential advantage.

There's good reason why MxR, MxM, Hoodman came into existence and others use KxS as well. I don't think anyone found a single "native" Express Card solution that worked reliably so no one is looking too hard in that area.

Why experiment when you can get one of the aforementioned adaptors and an ATP ProMax SDHC card which you KNOW works?

I can probably Google and list scores of cards people can try but the incentive isn't there for people to try. This goes for SDHC as well as "native" Express cards.

People may buy something out of desperation since nothing may be immediately available in an emergency and even if a single person tested and vetted it may not be enough for others to look that way.

People have gone through Sandisk, Transcend, ATP because they had to as previous SDHC cards manufacturers apparently changed production. That necessity resulted in quick testing and when a solution was found it was more widely tested and confirmed.

If there was success, you'd likely see it posted and if it were buried you'd find the results in a forum search.